The influence of a number of chemotherapeutic agents on the development of cutaneous squamous cell carcinomas and melanomas induced in the hairless mice by ultroviolet energy will be investigated. The chemicals to be studied are primarily cancer chemotherapeutic agents which not only have profound effects on cellular kinetics and melanocyte function but also are being utilized for prolonged periods in non-cancerous diseases. They will be administered systemically or topically depending on the methods utilized in human disease. The formation and growth of the cancers will be monitored. In addition, the acute and chronic effects of these chemicals on DNA synthesis, repair of ultraviolet-damaged DNA, and mitoses formation will be evaluated with radioactive tracer and colcemid techniques. Their influence on various phases of melanocyte function in normal, UV-stimulated, chemical carcinogen-stimulated and malignant melanoma tissue in vivo will be examined by microscopic techniques and dopa staining procedures.